1. FIELD OF THE INVENTION
This invention relates to an insulating apparatus for thermally insulating a dryer head journalled in a dryer section of a papermaking machine. More particularly, this invention relates to a stationary insulator for inhibiting the loss of heat from a drying cylinder of a papermaking machine.
2. INFORMATION DISCLOSURE STATEMENT
In the papermaking art, the formed, pressed web of paper is guided around a plurality of heated dryer drums in order to remove any excess moisture from the pressed web. Such dryer drums are heated by steam supplied to the inside of the rotatable dryer drums. Each dryer drum includes a cylindrical shell enclosed by opposed dryer heads rotatably journalled within support bearings. In use of the dryer drum, when steam is supplied to the inside of the rotatable dryer drum, heat is thermally conducted through the shell towards the paper web guided around the rotatable shell. However, a significant percentage of the thermal energy supplied to the dryer drum is conducted through the respective dryer heads and is lost by convection and radiation to the ambient surroundings.
In operation of a modern dryer section, the thermal energy requirements are very great and such heat losses through dryer heads can cause losses of up to 5% of the total energy requirements of such dryer sections. The provision of insulation adjacent to such dryer heads cause a resultant saving in the order of up to $33,000 per year.
Although several proposals have been set forth disclosing various means of fastening insulating covers to rotatable dryer heads, all of the prior art proposals show such insulating covers as being secured to the dryer head such that the insulating cover is rotatable.
Whereas, the provision of a rotatable insulator cover to a typical dryer drum having a 5 foot diameter may present relatively few problems, this is not the case when endeavoring to insulate the dryer heads of a Yankee Dryer or a machine-glazed (MG) cylinder which can be in the order of 8 to 25.5 feet in diameter. The provision of such a large rotating cover presents a potential hazard, particularly when applied to current Yankee and machine glazing dryer cylinders which operate at speeds of 3000 fpm or more. The rotating parts of the prior art insulator covers could cause harm or damage if they were to inadvertently contact personnel or adjacent equipment. In addition, in the event of an insulator cover rotating at this speed breaking away from a dryer, the results would be disastrous.
The present invention seeks to overcome the aforementioned potentially lethal situation by providing a stationary insulator having a sealing means disposed between the periphery of the insulator and the rotatable dryer head so that thermal losses are reduced and safety hazards are inhibited.
Therefore, it is a primary object of the present invention to provide an insulating apparatus for thermally insulating a dryer head which overcomes the aforementioned problems associated with the prior art proposals and which provides a significant contribution to the papermaking art.
Another object of the present invention is the provision of an insulating apparatus which includes a stationary insulator having a disc-shaped configuration with a central bore for the rotatable reception therein of the dryer head journal.
Another object of the present invention is the provision of an insulating apparatus which includes a peripheral sealing means which extends circumferentially around the insulator for inhibiting the flow of convection currents past the periphery of the insulator thereby reducing thermal losses through the head.
Another object of the present invention is the provision of an insulating apparatus which includes an air cap which is disposed adjacent to the dryer head with the air cap extending around a portion of the circumference of the dryer and a flexible seal which physically contacts, and sealingly engages, the air cap for inhibiting the flow of convection currents from the dryer head past the flexible seal.
Another object of the present invention is the provision of an insulating apparatus in which the diameter of the insulator is greater than the diameter of the dryer head such that when the air cap is retracted away from the dryer head, the flexible seal still maintains sealing engagement with the air cap.
Other objects and advantages of the present invention will be apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.